Sick seedlings -- brown spots and yellowing

hi guys i have some seedlings going and recently they began to develop some problems. let me first say that my grow setup was less than optimal. it was a rubbermaid box with good temps and decent (OK) ventilation and plenty of light. but i started the seedlings in four pots with MG premium potting soil. everything went fine at first. after about a week i transplanted the seedlings into individual pots (bottled water bottles with the tops cut off) since it wasnt good to have multiple plants per pot.

the plants did fine at first but after a little less than a week i started seeing a few small brown spots appear on various leaves in random spots. i also noticed at this time that many leaves were kinda pointed/curled downward instead of out to the sides like youd expect. some of the leaf veins began to appear a bit reddish, and after a few days passed the brown spots got worse and some of the leaves began to turn yellow and ugly, especially the older leaves and cotyledons. the newer leaves seem much less (if at all) affected by this affliction and growth rate seems close to normal.

i wasnt sure what the problem was but today i made a number of corrections. i finished up my big grow box that i had been building and put it into service. this one is much better in all aspects. same lighting (4 x 100 watt equivalent CFLs, with more ready to be installed later), more room, much better ventilation, air movement, and temp control. i took a trip up to a grow shop i discovered and loaded up on some stuff. got some FF ocean forest soil which i mixed in with big chunks of perlite, and then transplanted the plants into bigger and better pots with this new soil. i also discovered that the little pots i had been using did not appear to be draining well, so the plants might have been overwatered.

anyway i guess the point of the story is, what do you guys think could have caused these problems? overwatering, bad soil, or maybe a little of both? whats the chances of the plants making a full recovery? on the worst plant, probably only 40-50% of the leaf surfaces has turned brown or yellow, so there is plenty of green left and the new leaves look fine.

 

can anyone help please? some of my plants are getting worse and im afraid they may die if something doesnt change in the next day or two.. the leaves have brown (dead) spots and are yellowing and curling up quite a bit.. whats the problem and how can i solve it